1. Field of the Invention
This invention relates to solar collectors and in particular to a solar insolation collector which is incorporated into and integral with a structure.
2. Description of the Prior Art
Solar collectors are well known in the prior art and a variety of such devices have been developed for receiving insolation from the sun and heating a transfer fluid, such as air or water. Such transferred heat may be utilized for a variety of purposes, including space heating, heating of domestic hot water supplies, and absorption air conditioning. A type of prior art solar collector, commonly referred to as a "flat plate" collector, comprises a self-contained rectangular frame with a transparent outer cover of, for example, glass or clear plastic. A heat absorbing surface is provided below the cover and is typically in contact with conduits or other means for conveying the transfer fluid through the collector for receiving by convection the absorbed heat. The frame generally includes an inner cover with a thermally insulative material positioned between the inner cover and the collector plate for preventing heat loss from the collector assembly. Inlet and outlet ports are provided for communicating the heat transfer fluid with the collector.
A predetermined number of such flat plate collectors designed to provide sufficient heat absorption surface are generally placed on the finished, weathertight roof of a structure. However, because such prior art flat plate collectors are self-contained for manufacture elsewhere and installation on a finished roof structure, they tend to add considerably to the weight imposed upon such roof structures, thereby requiring support structures having greater load capacities at increased expense or, in the case of pre-existing structures not designed for the imposition of such additional loads, substantially limiting their application. A second major deficiency with such self-contained prior art flat plate collectors lies in their duplicity of several elements already present in the finished roof structures to which they are attached. For example, in such an installation both the flat plate collector and the roof structure include a weather-resistant outer material, a rigid self-supporting frame, and a layer of thermally insulative material. This duplicity of elements further increases the weight imposed by the flat plate solar collectors on the roof structure and necessitates a higher cost to the user.
It is known to incorporate portions of a solar collector into a roof structure. For example, the Cummings U.S. Pat. No. 4,201,188 shows a roof surface comprising an inclined light-transparent front wall with a cavity collector unit positioned therebehind in the attic of a structure. Corrugated heat traps are arrayed in the cavity collector unit. A roof structure incorporating a metal layer with water circulating channels positioned between a waterproofing layer and an insulating layer is disclosed in the Ronc U.S. Pat. No. 4,201,193. However, neither of the devices shown in the above patents provides all of the advantages of flat plate solar collectors including their relatively small space requirements and their absorption of both direct solar radiation and reradiation.
Another type of solar heat collector incorporated into a roof structure is exemplified in the Weinstein U.S. Pat. No. 4,141,339 wherein an air box of rigid insulated material is nested between framing members with a cover supported on their exterior faces. The box and glazing cover are movable relative to each other to accomodate differential thermal expansion and contraction. However, the last mentioned type of collector is susceptible to the inherent problems with utilizing air as the heat transfer medium, such as the requirement of providing sufficient air turbulence for good heat transfer and generally lower efficiencies in comparison with collectors utilizing water as the heat transfer fluid.
Prior art solar collectors have tended to be either relatively heavy, complex in structure and manufacture, or relatively inefficient as heat transfer devices.